Given the significance of HCO3- for autotrophic anammox bacteria (AnAOB), excessive HCO3- was always provided in anammox-related systems and engineering applications. However, its impact mechanism on anammox process at genome-level remains unknown. This study firstly established an anammox-centered coupling system that entails heterotrophic partial denitrification (PD) and hydrolytic acidification (A-PDHA) fed mainly with inorganic carbon (high HCO3- concentration and low C/N ratio). Metagenomic binning and metatranscriptomics analyses indicated that high HCO3- concentration enhanced expression of natural most efficient phosphoenolpyruvate (PEP) carboxylase within AnAOB, by up to 30.59 folds. This further induced AnAOB to achieve high-speed carbon-fixing reaction through cross-feeding of phosphate and PEP precursors with heterotrophs. Additionally, the enhanced activity of transporters and catalytic enzymes (up to 4949-fold) induced by low C/N ratio enabled heterotrophs to eliminate extracellular accumulated energy precursors mainly derived from carbon fixation products of AnAOB. This maintained high-speed carbon-fixing reaction within AnAOB and supplemented heterotrophs with organics. Moreover, assimilated energy precursors stimulated nitrogen metabolism enzymes, especially NO2- reductase (968.14 times), in heterotrophs. This established an energy-saving PD-A process mediated by interspecies NO shuttle. These variation resulted in efficient nitrogen removal (>95 %) and reduced external organic carbon demand (67 %) in A-PDHA system. This study unveils the great potential of an anammox-centered autotrophic-heterotrophic coupling system for achieving cost-effective nitrogen removal and enhancing carbon fixation under excessive HCO3- doses.

中文翻译：

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在以厌氧氨氧化为中心的偶联系统中，过量无机碳诱导的基因组协同高效固碳脱氮


鉴于 HCO3- 对自养厌氧氨氧化菌 （AnAOB） 的重要性，在厌氧氨氧化相关系统和工程应用中总是提供过量的 HCO3-。然而，它在基因组水平上对厌氧氨氧化过程的影响机制仍然未知。本研究首先建立了一个以厌氧氨氧化为中心的耦合系统，该系统需要异养部分反氮化 （PD） 和水解酸化 （A-PDHA），主要以无机碳 （高 HCO3- 浓度和低 C/N 比） 为原料。宏基因组分箱和宏转录组学分析表明，高 HCO3 浓度使 AnAOB 中天然最有效的磷酸烯醇式丙酮酸 （PEP） 羧化酶的表达增加了 30.59 倍。这进一步诱导 AnAOB 通过磷酸盐和 PEP 前驱体与异养生物的交叉进料实现高速固碳反应。此外，低 C/N 比诱导的转运蛋白和催化酶活性增强（高达 4949 倍）使异养生物能够消除主要来源于 AnAOB 碳固定产物的细胞外积累能量前体。这维持了 AnAOB 内的高速固碳反应，并用有机物补充了异养生物。此外，同化的能量前体刺激异养生物中的氮代谢酶，尤其是 NO2-还原酶 （968.14 倍）。这建立了一个由种间 NO 穿梭介导的节能 PD-A 过程。这些变化导致 A-PDHA 系统中的有效脱氮 （>95 %） 和减少外部有机碳需求 （67 %）。本研究揭示了以厌氧氨氧化为中心的自养-异养耦合系统的巨大潜力，该系统可在过量的 HCO3 剂量下实现具有成本效益的脱氮和增强碳固定。